Polypropylene wax and process for the production thereof

ABSTRACT

Polyolefin waxes are obtained in high yield by copolymerizing propylene with small amounts of other olefins in the presence of a catalyst composed of a metallocene of the formula I: ##STR1## and an alumoxane. The waxes are produced as compact, spherical particles having a narrow particle size distribution and high apparent density. In addition, the physical data of these waxes such as, for example, hardness, melting point, melt viscosity etc., are variable within wide limits. 
     The polymer chains are noteworthy for a homogeneous and uniform structure, the comonomer units being predominantly arranged individually between polypropylene blocks.

DESCRIPTION

The invention relates to a polypropylene wax whose polymer chains are ofhigh uniformity as regards chain length and chain structure.

The production of isotactic polyolefin waxes (isotactic index 80 to 85%,enthalpy of fusion 63 J/g, mixture of atactic and isotactic polyolefinchains) by means of supported catalysts, cocatalysts andstereoregulators at a temperature of over 95° C. is known (cf. DE3,148,229). Large amounts of hydrogen have to be employed as molar massregulator.

Furthermore, an MgCl₂ supported contact catalyst which results incrystalline PP waxes with a narrow molar mass distribution is also known(cf. JP 59/206,409). This catalyst, too, has the typical disadvantagesof catalyst systems which have been developed for the production ofhigh-molecular-weight polyolefins and consequently have a low activityin the production of low-molecular-weight polyolefins. Furthermore, hereagain, an undesirable mixture of isotactic and atactic chains is presentin the wax product.

Wax-type random ethylene copolymers which contain an α-olefin fractionof 1-15 mol % and which are produced using a catalyst system based onzirconium hydride metallocene/alumoxane (cf. JP 62/129,303) are alsoknown. Such metallocenes are not, however, suitable for producingisotactic polypropylene; in addition, their activity in polypropylenepolymerization is very low.

Owing to the low catalytic activity under the necessary reactionconditions, relatively high chlorine contents of, in some cases, over1000 ppm are found in the polymer waxes if the catalyst residues are notremoved by an expensive special post-treatment.

The use of metallocene/alumoxane catalyst systems has also been proposedfor the production of highly isotactic 1-olefin polymer waxes (cf. DE3,743,321).

Although it was possible to overcome the disadvantages of the processesdescribed above with this catalyst, the high isotacticity of theproducts resulted in the hardness of the waxes being extremely high, andthis is undesirable for a number of wax applications.

It is possible in principle to reduce the hardness by subsequentlyadding atactic poly-1-olefin wax. Apart from the high costs which areunacceptable and uneconomical on a large scale, this addition results innonuniform and sticky products.

There is consequently the object of finding a process with whichpolyolefin waxes having lower hardness can be produced usingmetallocene/alum oxane catalysts.

It was found that the object can be achieved by copolymerizing propylenewith other olefins in the presence of certain metallocene catalysts.

The invention consequently relates to a polypropylene wax composed of 80to 99.75% by weight, based on the total polymer, of propylene units and0.25 to 20% by weight, based on the total polymer, of units which arederived from ethylene or an olefin containing not less than 4 carbonatoms of the formula R¹⁵ --CH═CH--R¹⁶, in which R¹⁵ and R¹⁶ areidentical or different and are a hydrogen atom or an alkyl radicalcontaining 1 to 28 carbon atoms or R¹⁵ and R¹⁶ form a ring containing 4to 28 carbon atoms with the carbon atoms joining them, whichpolypropylene wax has a molar mass M_(w) of 1,000 to 50,000 g/mol, apolydispersity M_(w) /M_(n) of 1.8 to 5.0, a viscosity number of 2 to 60cm³ /g, a melting point of 50° to 250° C., an enthalpy of fusion ΔH ofless than 100 J/g, a dropping point of 60° to 160° C., a melt viscosityat 170° C. of 100 to 20,000 mPa.s and a regular distribution of thecomonomer units in the polymer chain, the mean block length n being lessthan 1.25.

The invention furthermore relates to a process for the production of thepolypropylene wax as claimed in claim 1 by polymerizing 70 to 99.9% byweight, based on the total amount of the monomers, of propylene and 0.1to 30% by weight, based on the total amount of the monomers, of not lessthan one representative of the group comprising ethylene and olefinscontaining not less than 4 carbon atoms of the formula R¹⁵ --CH═CH--R¹⁶,in which R¹⁵ and R¹⁶ have the meaning stated in claim 1, at atemperature of -60° C. to 100° C., at a pressure of 0.5 to 120 bar, insolution, in suspension or in the gas phase, in the presence of hydrogenas a molar mass regulator and of a catalyst which is composed of ametallocene and an alumoxane wherein the hydrogen partial pressure is0.05 to 50 bar and the molar ratio of olefin to hydrogen is 3 to3,000:1, and wherein the metallocene is a compound of the formula I:##STR2## in which

M¹ is a metal of the group IVb, Vb or VIb of the periodic system,

R¹ and R² are identical or different and are a hydrogen atom, a (C₁-C₁₀)alkyl group, a (C₁ -C₁₀)alkoxy group, a (C₆ -C₁₀)aryl group, a (C₆-C₁₀)aryloxy group, a (C₂ -C₁₀)alkenyl group, a (C₇ -C₄₀)arylalkylgroup, a (C₇ -C₄₀)alkylaryl group, a (C₈ -C₄₀)arylalkenyl group or ahalogen atom,

R³, R⁴, R⁵ and R⁶ are identical or different and are a hydrogen atom, ahalogen atom, a (C₁ -C₁₀)alkyl group, a (C₁ -C₁₀)alkoxy group, a (C₆-C₁₀)aryl group, or an --NR₂ ¹⁰, --SR¹⁰, --OSiR₃ ¹⁰,--SiR₃ ¹⁰, or --PR₂¹⁰ radical, in which R¹⁰ is a (C₁ -C₁₀)alkyl group, a (C₆ -C₁₀)arylgroup or alternatively, in the case of radicals containing silicon orphosphorus, a halogen atom, or two adjacent R³, R⁴, R⁵ or R⁶ radicalseach form a ring with the carbon atoms joining them,

R⁷ is ##STR3## ═BR¹¹, ═AlR¹¹, --Ge--, --Sn--, --O--, --S--, ═SO, ═SO₂,═NR¹¹, ═CO, ═PR¹¹ or ═P(O)R¹¹ where

R¹¹, R¹² and R¹³ are identical or different and are a hydrogen atom, ahalogen atom, a (C₁ -C₃₀)alkyl group, a (C₁ -C₁₀)fluoroalkyl group, a(C₆ -C₁₀)aryl group, a (C₆ -C₁₀)fluoroaryl group, a (C₁ -C₁₀)alkoxygroup, a (C₂ -C₁₀)alkenyl group, a (C₇ -C₄₀)arylalkyl group, a (C₈-C₄₀)arylalkenyl group, a (C₇ -C₄₀)alkylaryl group, or R¹¹ and R¹² orR¹¹ and R¹³ in each case form a ring with the atoms joining them,

M² is silicon, germanium or tin,

R⁸ and R⁹ are identical or different and have the meaning stated forR¹¹,

m and n are identical or different and are zero, 1 or 2, m plus n beingzero, 1 or 2, and the alumoxane is a compound of the formula (II):##STR4## for the linear type and/or of the formula (III) ##STR5## forthe cyclic type, R¹⁴ being a (C₁ -C₆)alkyl group in the formulae (II)and (III) and p being an integer from 2 to 50.

The polypropylene wax according to the invention is composed of 80 to99.75, preferably 90 to 99.5% by weight, based on the total polymer, ofpropylene units and of 0.25 to 20, preferably 0.5 to 15% by weight,based on the total polymer, of units which are derived from ethylene oran olefin containing at least 4 carbon atoms of the formula R¹⁵--CH═CH--R¹⁶. In this formula, R¹⁵ and R¹⁶ are identical or differentand are a hydrogen atom or an alkyl radical containing 1 to 28 carbonatoms. R¹⁵ and R¹⁶ may, however, also form a ring containing 4 to 28carbon atoms with the carbon atoms joining them. Examples of sucholefins are 1-butene, 1-hexene, 4-methyl-1-pentene, 1-pentene, 1-octene,norbornene, norbornadiene, 6-pentene, cyclohexene or cyclooctene.

Preferred copolymer waxes are propylene/ethylene, propylene/1-hexene,propylene/1-butene and propylene/4-methyl-1-pentene polymers.

Copolymers of three different monomers are preferablypropylene/ethylene/1-hexene and propylene/ethylene/1-butene terpolymerwaxes.

The copolymer wax according to the invention has a molar mass M_(w) of1,000 to 50,000 g/mol, preferably 8,000 to 45,000 g/mol, apolydispersity M_(w) /M_(n) of 1.8 to 5.0, preferably 2.0 to 4.0, aviscosity number of 2 to 60 cm³ /g, preferably 10 to 50 cm³ /g, amelting point of 50° to 150° C., preferably 70° to 140° C., an enthalpyfusion ΔH of less than 100 J/g, a dropping point of 60° to 160° C.,preferably 80° to 150° C., a melt viscosity of 100 to 20,000 mPa.s,preferably 120 to 7,000 mPa.s, at 170° C. and a regular distribution ofthe comonomer units in the polymer chain, the medium comonomer blocklength n being less than 1.25, preferably less than 1.2.

The catalyst to be used for the process according to the invention iscomposed of an alumoxane and a metallocene of the formula I: ##STR6## Informula I, M¹ is a metal of the group IVb, Vb or VIb of the periodicsystem, for example titanium, zirconium, hafnium, vanadium, niobium,tantalum, chromium, molybdenum or tungsten, preferably zirconium andhafnium.

R¹ and R² are identical or different and are a hydrogen atom, a (C₁-C₁₀)-, preferably a (C₁ -C₃)alkyl group, a (C₁ -C₁₀)-, preferably a (C₁-C₃)alkoxy group, a (C₆ -C₁₀)-, preferably a (C₆ -C₈)aryl group, a (C₆-C₁₀), preferably a (C₆ -C₈)aryloxy group, a (C₂ -C₁₀)-, preferably a(C₂ -C₄)alkenyl group, a (C₇ -C₄₀)-, preferably a (C₇ -C₁₀)arylalkylgroup, a (C₇ -C₄₀)-, preferably a (C₇ -C₁₂)alkylaryl group, a (C₈-C₄₀)-, preferably a (C₈ -C₁₂)arylalkenyl group or a halogen atom,preferably chlorine.

R³, R⁴, R⁵ and R⁶ are identical or different and are a hydrogen atom, ahalogen atom, preferably a fluorine, chlorine or bromine atom, a (C₁-C₁₀)-, preferably a (C₁ -C₃)alkyl group, a (C₆ -C₁₀), preferably a (C₆-C₈)aryl group, a (C₁ -C₁₀)-, preferably a (C₁ -C₃)alkoxy group, or an--NR₂ ¹⁰, --SR¹⁰, --OSiR₃ ¹⁰, --SiR₃ ¹⁰, or --PR₂ ¹⁰ radical, in whichR¹⁰ is a (C₁ -C₁₀), preferably a (C₁ -C₃)alkyl group or a (C₆ -C₁₀)-,preferably a (C₆ -C₈)aryl group, or alternatively, in the case ofradicals containing silicon or phosphorus, a halogen atom, preferably achlorine atom, or two adjacent radicals R³, R⁴, R⁵ or R⁶ each form aring with the carbon atoms joining them. Particularly preferred ligandsare indenyl, fluorenyl and cyclopentadienyl.

R⁷ is ##STR7## ═BR¹¹, ═AlR¹¹, --Ge--, --Sn--, --O--, --S--, ═SO, ═SO₂,═NR¹¹, ═CO, ═PR¹¹ or ═P(O)R¹¹, where R¹¹, R¹² and R¹³ are identical ordifferent and are a hydrogen atom, a halogen atom, a (C₁ -C₃₀)-,preferably a (C₁ -C₄)alkyl group, in particular a methyl group, a (C₁-C₁₀)fluoroalkyl group, preferably a CF₃ group, a (C₆ -C₁₀)fluoroarylgroup, preferably a pentafluorophenyl group, a (C₆ -C₁₀), preferably a(C₆ -C₈)aryl group, a (C₁ -C₁₀), preferably a (C₁ -C₄)alkoxy group, inparticular a methoxy group, a (C₂ -C₁₀), preferably (C₂ -C₄)alkenylgroup, a (C₇ -C₄₀), preferably a (C₇ -C₁₀)arylalkyl group, a (C₈ -C₄₀)-,preferably a (C₈ -C₁₂)arylalkenyl group or a (C.sub. 7 -C₄₀), preferablya (C₇ -C₁₂)alkylaryl group, or R¹¹ and R¹² or R¹¹ and R¹³ together formin each case a ring with the atoms joining them.

M² is silicon, germanium or tin, preferably silicon and germanium.

R⁷ is preferably ═CR¹¹ R¹², ═SiR¹¹ R¹², ═GeR¹¹ R¹², --O--, --S--, ═SO,═PR¹¹ or ═P(O)R¹¹.

R⁸ and R⁹ are identical or different and have the meaning stated forR¹¹.

m and n are identical or different and are zero, 1 or 2, preferably zeroor 1, m plus n being zero, 1 or 2, preferably zero or 1.

The metallocenes described above can be prepared by the followinggeneral reaction scheme: ##STR8##

Metallocene compounds which are preferably employed are

dialkylsilylbisindenylzirconium dichloride,

alkylalkylenebisindenylzirconium dichloride,

alkylenebisindenylzirconium dichloride,

diarylalkylenebisindenylzirconium dichloride,

alkylenebisindenylhafnium dichloride,

diarylsilylbisindenylzirconium dichloride,

(aryl)(alkyl)bisindenylzirconium dichloride,

dialkylgermylbisindenylzirconium dichloride,

(alkyl)(alkenyl)silylbisindenylzirconium dichloride and

(aryl)(alkenyl)silylbisindenylzirconium dichloride.

In this connection, the following are particularly preferred:

dimethylsilylbisindenylzirconium dichloride,

ethylenebisindenylzirconium dichloride,

diphenylsilylbisindenylzirconium dichloride,

dimethylgermylbisindenylzirconium dichloride,

(phenyl)(vinyl)silylbisindenylzirconium dichloride and

ethylenebisindenylhafnium dichloride.

The cocatalyst is an alumoxane of the formula II: ##STR9## for thelinear type and/or of the formula (III): ##STR10## for the cyclic type.In these formulae, R¹⁴ is a (C₁ -C₆)alkyl group, preferably methyl,ethyl or isobutyl, in particular methyl, and p is an integer from 2 to50, preferably 5 to 40. The precise structure of the alumoxane is,however, not known.

The alumoxane can be prepared in various ways.

One possibility is to add water carefully to a dilute solution oftrialkylaluminum, the solution of the trialkylaluminum, preferablytrimethylaluminum, and the water each being introduced in small portionsinto a larger amount of an inert solvent which has been taken and thecessation of gas development always being awaited inbetween.

In another process, finely powdered copper sulfate pentahydrate issuspended in toluene and mixed in a glass flask under inert gas at about-20° C. with enough trialkylaluminum for about 1 mol of CuSO₄.5H₂ O tobe available for every 4 Al atoms. After slow hydrolysis involvingalkane detachment, the reaction mixture is left for 24 to 48 hours atroom temperature, it possibly being necessary to cool it in order toprevent the temperature rising above 30° C. Then the alum oxanedissolved in the toluene is filtered off from the copper sulfate and thesolution is evaporated down in vacuo. It is assumed that, in thisprocess of preparation, the low-molecular-weight alumoxane condense toform higher oligomers with the detachment of trialkylaluminum.

Furthermore, alumoxane are obtained if dissolved trialkylaluminum,preferably trimethylaluminum, is reacted with aluminum salts, preferablyaluminum sulfate, containing water of crystallization at a temperatureof -20° to 100° C. in an inert aliphatic or aromatic solvent, preferablyheptane or toluene. In this case, the volumetric ratio between solventand the alkylaluminum used is 1:1 to 50:1--preferably 5:1--and thereaction time, which can be monitored by the detachment of the alkane,is 1 to 200 hours--preferably 10 to 40 hours.

Among the aluminum salts containing water of crystallization, inparticular those are used which have a high content of water ofcrystallization. Particularly preferred is aluminum sulfate hydrate,especially the compounds Al₂ (SO₄)₃.16H₂ O and Al₂ (SO₄)₃.18H₂ O, whichhave the particularly high content of water of crystallization of 16 or18 mol of H₂ O/mol of Al₂ (SO₄)₃, respectively.

A further variant of the preparation of alumoxane is to dissolvetrialkylaluminum, preferably trimethylaluminum, in the suspending agentcontained in the polymerization vessel, preferably in the liquidmonomer, in heptane or toluene and then to react the aluminum compoundwith water.

In addition to the processes described above for preparing alumoxanethere are further processes which can be used. Regardless of the type ofpreparation, a varying content of unreacted trialkylaluminum, which ispresent in free form or as an adduct, is common to all alumoxanesolutions.

It is possible to pre-activate the metallocene with an alumoxane of theformula (II) and/or (III) before use in the polymerization reaction.This markedly increases the polymerization activity and improves theparticle morphology.

The transition metal compound is preactivated in solution. In thisconnection, the metallocene is preferably dissolved in a solution of thealumoxane in an inert hydrocarbon. A suitable inert hydrocarbon is analiphatic or aromatic hydrocarbon.

Preferably toluene is employed. The concentration of the alumoxane inthe solution is in the range from approximately 1 part by weight up tothe saturation limit, preferably from 5 to 30% by weight, based in allcases on the total solution. The metallocene may be employed in the sameconcentration, preferably, however, it is employed in an amount of 10⁻⁴-1 mol per mol of alumoxane. The preactivation time is 5 minutes to 60hours, preferably 5 to 60 minutes. A temperature of -78° C. to 100° C.,preferably 0° to 70° C., is employed.

The polymerization is carried out in a known manner in solution, insuspension or in the gas phase, continuously or batchwise, in one stepor several steps at a temperature of -60+ to 150° C., preferably 0° to80° C. The polymerization involves propylene and, as comonomer, at leastone member of the group consisting of ethylene and olefins containing atleast 4 carbon atoms of the formula R¹⁵ --CH═CH--R¹⁶. In this formula,R¹⁵ and R¹⁶ have the meaning already stated. 70 to 99.9, preferably 80to 99.7% by weight, based on the total amount of the monomers, ofpropylene and 0.1 to 30, preferably 0.3 to 20% by weight, based on thetotal amount of the monomers, of at least one comonomer are employed.

Hydrogen is added as molar mass regulator, the hydrogen partial pressurebeing in the range from 0.05 to 50 bar, preferably 0.1 to 25 bar, inparticular 0.2 to 10 bar. The molar ratio of the olefins to hydrogen is3 to 3,000, preferably 6 to 1,500, in particular 15 to 300.

The total pressure in the polymerization system is 0.5 to 120 bar.Polymerization in the industrially particularly attractive pressurerange from 5 to 64 bar is preferred.

In this connection, the metallocene compound is employed in aconcentration, based on the transition metal, of 10³¹ 1 to 10⁻⁷,preferably 10⁻⁴ to 10⁻⁶ mol of transition metal per dm³ of solvent orper dm³ of reactor volume. The alumoxane is used in a concentration of10⁻⁵ to 10⁻¹ mol, preferably 10⁻⁴ to 10⁻² mol per dm³ of solvent or perdm³ of reactor volume, respectively. In principle, however, even higherconcentrations are possible.

If the polymerization is carried out as a suspension or solutionpolymerization, an inert solvent which is normal for the Zieglerlow-pressure process is used. For example, an aliphatic orcycloaliphatic hydrocarbon is employed; as such, mention may be made,for example, of butane, pentane, hexane, heptane, isooctane, cyclohexaneand methylcyclohexane.

Furthermore, a gasoline or hydrogenated diesel oil fraction may be used.Toluene is also useable. Preferably, polymerization is carried out inthe liquid monomer. If inert solvents are used, the monomers are addedin gaseous or liquid form. If only one monomer is used as suspendingagent, the comonomer is, or the comonomers are, added in gaseous orliquid form. It is furthermore possible to polymerize in a mixture ofdifferent monomers as suspending agent; a further monomer can then beadded in liquid or gaseous form.

The polymerization time is indefinite since the catalyst system to beused according to the invention exhibits only a slight time-dependentdrop in the polymerization activity.

Chemically highly uniform copolymer waxes can be produced by the processaccording to the invention.

In general, the chain ends are constructed of saturated hydrocarbongroups. The polydispersity M_(w) /M_(n) is extremely narrow, withtypical values of 2.0-3.0. The comonomer or the comonomers are almostexclusively incorporated individually between polypropylene blocks, andthis results in an optimum reduction in the crystallinity and hardnessof the copolymer waxes. Associated with this is a reduction in theenthalpy of fusion and enthalpy of crystallization, and also of themelting point and crystallization point. Depending on the process, theseparameters, and in addition the melt viscosity, can be controlledprecisely over a wide range by varying the amount of hydrogen and byvarying the comonomers. In addition, colorless, highly transparent waxescan also be produced by means of the process according to the invention.The polymer powders produced according to the invention are composed ofnonadhering, compact spherical particles having a narrow particle sizedistribution and high apparent density. The wax powder is noteworthy forits very good free-flowing property and can consequently be handled inan optimum manner.

The catalyst activities are very high, and this means low catalystresidue contents in the polymer for high space-time yields.

The following examples are intended to explain the invention in moredetail.

Key to symbols

    __________________________________________________________________________    VN = Viscosity number in cm.sup.3 /g                                          M.sub.w = Weight average of molar mass                                                              determined by gel                                       M.sub.n = Number average of molar mass                                                              permeation chromatography                               M.sub.w /M.sub.n = Polydispersity                                                                   (numerical data in g/mol)                               MV = Melt viscosity determined by means of rotational                         viscometer at 170° C.                                                  AD = Apparent density of the polymer powder in g/dm.sup.3                     n.sub.PP = Medium polypropylene block length                                  n.sub.PE = Medium polyethylene block length                                   n.sub.PH = Medium polyhexene block length                                     n.sub.PB = Medium polybutene block length                                     N.sub.PMP = Medium poly-4-methy-1-pentene block length                        __________________________________________________________________________

(the block lengths were determined by means of ¹³ C NMR spectroscopy)

Melting points, crystallization points, their full widths at halfmaximum, the enthalpies of fusion and crystallization, and also theglass transition temperatures (Tg) were determined by DSC measurements(heating/cooling rate 20° C./min).

EXAMPLES 1-16

A dry 16 dm³ vessel was flushed with nitrogen and filled with 40 Ndm³(equivalent to 2.5 bar) of hydrogen and also with 10 dm³ of liquidpropylene. Then 30 cm³ of toluenic methylalumoxane solution (equivalentto 40 mmol of Al, average degree of oligomerization of themethylalumoxane n=20) and also 25% by weight of the desired total amountof ethylene (see Table 1 for amounts) were added and the mixture wasstirred for 15 minutes at 30° C.

In parallel with this, the amount shown in Table 1 of the zirconocenedimethylsilylbisindenylzirconium dichloride was dissolved in 15 cm³ oftoluenic methylalumoxane solution (20 mmol of Al) and preactivated bybeing allowed to stand for 15 minutes. The orange-red solution was thenintroduced into the vessel. The polymerization system was brought to thepolymerization temperature shown in Table 1 and was kept at thistemperature by suitable cooling during the polymerization time (Table1). The remaining amount of ethylene was added uniformly during thepolymerization time.

Product amounts, metallocene activities and also the ethylene content ofthe polymers produced are summarized in Table 1. The product propertiesare to be found in Table 2.

EXAMPLES 17-19

The procedure was analogous to that of Examples 1-16, but the amount ofhydrogen used as molar mass regulator was varied. Instead of 40 Ndm³,the amounts specified in Table 3 were added. The polymerizationconditions are to be found in Table 3 and the product properties inTable 4.

EXAMPLES 20-24

The procedure was analogous to that in Examples 1-16, but themetallocenes ethylenebisindenylzirconium dichloride (Example 20),diphenylsilylbisindenylzirconium dichloride (Example 21),dimethylgermylbisindenylzirconium dichloride (Example 22),ethylenebisindenylhafnium dichloride (Example 23) and(vinyl)(phenyl)silylbisindenylzirconium dichloride (Example 24) wereused instead of dimethylsilylbisindenylzirconium dichloride. Thepolymerization conditions are to be found in Table 5 and the productproperties in Table 6.

EXAMPLES 25-27

The procedure was analogous to that of Examples 1-16, but the comonomers1-hexene (Example 25), 1-butene (Example 26) and 4-methyl-1-pentene(Example 27) were used instead of the comonomer ethylene. Thepolymerization conditions are to be found in Table 7 and the productproperties in Table 8.

EXAMPLE 28

A dry 16 dm³ vessel was flushed with nitrogen and filled with 10 dm³ ofliquid propylene. Then 30 cm³ of toluenic methylalumoxane solution(equivalent to 40 mmol of Al, average degree of oligomerization of themethylalum oxane n=20) were added and the mixture was stirred for 15minutes.

In parallel with this, 8.5 mg (0.019 mmol) ofdimethylsilylbisindenylzirconium dichloride were dissolved in 15 cm³ oftoluenic methylalumoxane solution (20 mmol of Al). After 15 minutes, theorange-red solution was introduced into the vessel. The polymerizationsystem was brought to 50° C. and then 85 g of ethylene were continuouslyadding during the 60-minute polymerization time. 1.1 kg of polymerpowder, equivalent to a metallocene activity of 129.4 kg of polymer/g ofcatalyst×h were obtained.

The ethylene incorporated was 7.1% by weight.

Block length: n_(PP) =9.2, nhd PE=1.05, VN=39 cm³ /g; M_(w) =24,750,M_(n) =9,850, M_(w) /M_(n) =2.5; AD=330 g/dm³ ; MV=1,350 mPa.s;

Dropping point 128° C.; melting point 108° C.,

Crystallization point 69° C., glass transition temperature -24° C.,

Enthalpy of fusion 52.8 J/g, enthalpy of crystallization -40.1 J/g.

COMPARISON EXAMPLE A

A dry 16 dm³ vessel was flushed with nitrogen and filled with 40 Ndm³(equivalent to 2.5 bar) of hydrogen, with 10 dm³ of liquid propylene and140 g of ethylene. Then 30 cm³ of toluenic methylalumoxane solution(equivalent to 40 mmol of Al, average degree of oligomerization of thealuminoxane n=20) were added and the mixture was stirred for 15 minutes.

In parallel with this, 8.5 mg (0.019 mmol) ofdimethylsilylbisindenylzirconium dichloride were dissolved in 15 cm³ oftoluenic methylalumoxane solution (20 mmol of Al). After 15 minutes, theorange-red solution was introduced into the vessel. Polymerization wascarried out for 60 minutes at 50° C. 2.0 kg of polymer powder wereobtained, equivalent to a metallocene activity of 235.3 kg of polymer/gof catalyst×h. The ethylene incorporated was 6.8% by weight. VN=38 cm³/g, M_(w) =24,950, M_(n) =10,150, M_(w) /M_(n) =2.5, AD 310 g/dm³,NV=1,220 mPa.s;

dropping point 141° C.; melting point 128° C.,

crystallization point 91° C., glass transition temperature -32° C.,

enthalpy of fusion 63.5 J/g, enthalpy of crystallization -50.7 J/g.

Taking the entire amount of comonomer results in a considerablydifferent product from that which is obtained by taking 25% of the totalamount of monomer and continuously adding the remaining comonomer duringthe polymerization (Examples 8 and 9) or which is obtained byexclusively adding the comonomer during the polymerization (Example 28).Dropping point, melting point, crystallization point, enthalpy of fusionand also enthalpy of crystallization are considerably higher. Accordingto ¹³ C NMR, a product with a higher medium block length n_(PE) isobtained.

EXAMPLE 29

A dry 16 dm³ vessel was flushed with nitrogen and filled with 40 Ndm³(equivalent to 2.5 bar) of hydrogen, with 10 dm³ of liquid propylene,with 300 g of 1-hexene and 17.5 g of ethylene. Then 30 cm³ of toluenicmethylalumoxane solution (equivalent to 40 mmol of Al, average degree ofoligomerization n=20) were added and the mixture was stirred for 15minutes.

In parallel with this, 8.5 mg (0.019 mmol) ofdimethylsilylbisindenylzirconium dichloride were dissolved in 15 cm³ oftoluenic methylalumoxane solution (20 mmol of Al).

After 15 minutes, the orange-red solution was introduced into thevessel. Polymerization was carried out for 60 minutes at 60° C., 52.5 gof ethylene being added continuously. 2.1 kg of polymer powder,equivalent to a metallocene activity of 247.0 kg of polymer/g ofcatalyst×h, were obtained.

The polymer contained 2.6% by weight of hexene units, 2.5% by weight ofethylene units and 94.9% by weight of propylene units. Mean block lengthof the copolymers, n_(PH) =1.0: n_(PE) =1.02; VN=29.1 cm³ /g, M_(w)=17,400, M_(n) =8,050, M_(w) /M_(n) =2.2; AD=410 g/dm³ ; MV=760 MPa.s;dropping point 118° C., melting point 106° C., crystallization point 68°C., enthalpy of fusion 70.4 J/g, enthalpy of crystallization -52.6 J/g,glass transition temperature -22° C.

EXAMPLE 30

The procedure was as in Example 29, but 500 g of 1-butene were takeninstead of 300 g of 1-hexene. 1.92 kg of polymer powder, equivalent to ametallocene activity of 225.9 kg of polymer/g of catalyst×h, wereobtained. The polymer contained 4.1% by weight of butene units, 2.9% byweight of ethylene units and 93.0% by weight of propylene units. Themean block lengths of the copolymers were: n_(PE) =1.04 and n_(PB)=1.09. VN=30 cm³ /g; M_(w) =19,100, M_(n) =9,100, M_(w) /M_(n) =2.1;AD=370 g/dm³, MV=760 mPa.s; dropping point 120° C., melting point 110°C., crystallization point 70° C., enthalpy of fusion 76.1 J/g, enthalpyof crystallization -62.0 J/g, glass transition temperature -21° C.

                                      TABLE 1                                     __________________________________________________________________________    Examples 1-16                                                                 (Polymerization data)                                                                                                 Metallocene                                             Polymerization                                                                        Polymerization                                                                        Amount of                                                                           activity                                                                             Content of                          g Ethylene                                                                          mg/(mmol)                                                                            temperature                                                                           time    product                                                                             [kg polymer/                                                                         comonomer units                Example                                                                            total zirconocene                                                                          [°C.]                                                                          [minutes]                                                                             [kg]  g cat × h]                                                                     [% by weight]                  __________________________________________________________________________    1     12   12.0 (0,027)                                                                         60      60      2.25  187.5  0.5                            2     26   15.5 (0,035)                                                                         "       45      2.95  253.8  0.7                            3     45   11.8 (0,026)                                                                         "       50      2.16  219.7  2.0                            4     70    6.9 (0,015)                                                                         "       60      2.82  408.7  2.4                            5     80    8.6 (0,019)                                                                         "       "       2.88  334.9  2.6                            6    100    8.1 (0,018)                                                                         "       "       1.73  213.6  5.6                            7    110   13.4 (0,030)                                                                         "       "       2.30  171.6  4.6                            8    150    7.8 (0,017)                                                                         "       75      1.97  202.1  7.3                            9    160    6.8 (0,015)                                                                         "       "       2.32  272.9  6.5                            10   200    6.8 (0,015)                                                                         "       60      1.61  236.8  12.0                           11   300    7.8 (0,017)                                                                         "       "       1.90  243.6  15.1                           12    40   11.6 (0,026)                                                                         50      "       2.21  190.5  1.7                            13    80   12.1 (0,027)                                                                         "       30      1.45  239.7  5.5                            14   100   11.3 (0,025)                                                                         "       60      1.60  141.6  6.2                            15   125   14.1 (0,031)                                                                         "       57      1.85  131.2  6.5                            16   140    8.4 (0,019)                                                                         "       60      1.50  178.6  8.8                            __________________________________________________________________________

                                      TABLE 2                                     __________________________________________________________________________    Examples 1-16                                                                 (Product properties)                                                                                                                    Enthalpy                                        Drop-                                                                             Mean        Crystal-                                                                           Glass                                                                             Enthalpy                                                                           of                  VN       M.sub.w                                                                           M.sub.n                                                                              AD      ping                                                                              block  Melting                                                                            lization                                                                           trans.                                                                            of   crystal-            [cm.sup.3 /                                                                            [g/ [g/ M.sub.w /                                                                        [g/ MV  point                                                                             length point                                                                              point                                                                              temp.                                                                             fusion                                                                             lization            Example                                                                            g]  mol]                                                                              mol]                                                                              M.sub.n                                                                          dm.sup.3 ]                                                                        [mPa.s]                                                                           [°C.]                                                                      - n.sub.PP                                                                        - n.sub.PE                                                                       [°C.]                                                                       [°C.]                                                                       [°C.]                                                                      [J/g]                                                                              [J/g]               __________________________________________________________________________     1   22  12500                                                                              5850                                                                             2.1                                                                              420  300                                                                              146 130 1.0                                                                              137  100      98.5 -90.0                2   21  12300                                                                              5670                                                                             2.2                                                                              415  300                                                                              143 90  1.0                                                                              135  98       93.2 -91.7                3   25  13900                                                                              6590                                                                             2.1                                                                              525  500                                                                              134 28.7                                                                              1.01                                                                             124  86       84.4 -74.6                4   26  15350                                                                              7200                                                                             2.1                                                                              490  580                                                                              133 25.5                                                                              1.02                                                                             122  82   -18 85.4 -73.6                5   25  14750                                                                              6700                                                                             2.2                                                                              460  450                                                                              130 25.0                                                                              1.02                                                                             121  81   -18 83.2 -72.9                6   30  18700                                                                              7360                                                                             2.5                                                                              325  800                                                                              120 11.8                                                                              1.04                                                                             108  70   -20 70.0 -53.3                7   29  17750                                                                              8050                                                                             2.2                                                                              420  740                                                                              120 14.5                                                                              1.02                                                                             108  69   -20 74.3 -60.1                8   36  22600                                                                              8670                                                                             2.6                                                                              420 1640                                                                              118 9.4 1.10                                                                              93  56   -25 53.7 -38.5                9   34  21200                                                                              9800                                                                             2.2                                                                              470 1150                                                                              118 9.9 1.03                                                                              98  57   -23 61.6 -45.8               10   45  31750                                                                             15120                                                                             2.1                                                                              460 3450                                                                              101 4.9 1.05                                                                              88  46   -26 39.2 -29.1               11   51  43250                                                                             18800                                                                             2.3                                                                              450 5820                                                                               94 3.6 1.08                                                                              81  43   -30 24.9 -19.1               12   29  18350                                                                              7470                                                                             2.4                                                                              325  700                                                                              140 39.0                                                                              1.03                                                                             131  96    - 9                                                                              97.5 -82.8               13   35  21600                                                                              8960                                                                             2.4                                                                              370 1450                                                                              125 11.6                                                                              1.02                                                                             104  64   -19 68.4 -52.0               14   38  22850                                                                             10000                                                                             2.3                                                                              440 1570                                                                              128 10.5                                                                              1.02                                                                             100  60   -21 64.4 -49.0               15   38  22100                                                                              8740                                                                             2.5                                                                              400 1930                                                                              129 10.0                                                                              1.03                                                                              99  58   -21 61.8 -46.3               16   42  26100                                                                             12150                                                                             2.1                                                                              300 2800                                                                              118 7.3 1.02                                                                              86  48   -25 56.0 -34.3               __________________________________________________________________________

                                      TABLE 3                                     __________________________________________________________________________    Examples 17- 19                                                               (Polymerization data)                                                                                            Polymer-    Metallocene                    Amount of                  Polymerization                                                                        ization                                                                             Amount of                                                                           activity                                                                             Content of              hydrogen            mg (mmol)                                                                            temperature                                                                           time  product                                                                             [kg polymer/                                                                         comonomer units         Example                                                                            [Ndm.sup.3 ]                                                                      [bar]                                                                            g Comonomer                                                                           zirconocene                                                                          [°C.]                                                                          [minutes]                                                                           [kg]  g cat × h]                                                                     [% by                   __________________________________________________________________________                                                          weight]                 17    8  0.5                                                                               80 g Ethylene                                                                         9.5 (0.021)                                                                         60      60    3.57  375.8  2.1                     18   16  1   80 g Ethylene                                                                        11.2 (0.025)                                                                         60      45    3.69  439.3  2.1                     19   80  5  140 g Ethylene                                                                         6.5 (0.015)                                                                         60      60    2.80  430.8  4.8                     __________________________________________________________________________

                                      TABLE 4                                     __________________________________________________________________________    Example 17-19                                                                 (Product properties)                                                                                                                    Enthalpy                                        Drop-                                                                             Mean        Crystal-                                                                           Glass                                                                             Enthalpy                                                                           of                  VN       M.sub.w                                                                           M.sub.n                                                                              AD      ping                                                                              block  Melting                                                                            lization                                                                           trans.                                                                            of   crystal-            [cm.sup.3 /                                                                            [g/ [g/ M.sub.w /                                                                        [g/ MV  point                                                                             length point                                                                              point                                                                              temp.                                                                             fusion                                                                             lization            Example                                                                            g]  mol]                                                                              mol]                                                                              M.sub.n                                                                          dm.sup.3 ]                                                                        [mPa.s]                                                                           [°C.]                                                                      - n.sub.PP                                                                        - n.sub.PE                                                                       [°C.]                                                                       [°C.]                                                                       [°C.]                                                                      [J/g]                                                                              [J/g]               __________________________________________________________________________    17   48.1                                                                              34750                                                                             15050                                                                             2.3                                                                              510 4590                                                                              133 29.6                                                                              1.01                                                                             121  86   -14 79.2 -68.4               18   37.0                                                                              23850                                                                              9930                                                                             2.4                                                                              500 1820                                                                              132 32.1                                                                              1.03                                                                             123  79   -15 82.3 -71.2               19   24.2                                                                              12600                                                                              5930                                                                             2.1                                                                              480  420                                                                              123 13.2                                                                              1.05                                                                             109  71   -21 74.9 -58.2               __________________________________________________________________________

                                      TABLE 5                                     __________________________________________________________________________    Examples 20- 24                                                               (Polymerization data)                                                                                                Polymer-                                                                           Amount                                                                             Metallocene                                                                          Comonomer                                                    ization                                                                            of   activity                                                                             content                    mg (mmol)                Polymerization                                                                         time product                                                                            [kg polymer/                                                                         [% by                 Example                                                                            Metallocene compound                                                                           g Comonomer                                                                           temperature [°C.]                                                               [minutes]                                                                          [kg] g cat × h]                                                                     weight]               __________________________________________________________________________    20   8.3 (0.020) Ethylenebisindenyl-                                                                100 g Ethylene                                                                        60       60   2.48 298.8  3.7                        zirconium dichloride                                                     21   25.6 (0.045) Diphenylsilylbis-                                                                 110 g Ethylene                                                                        60       60   2.06  80.5  5.1                        indenylzirconium dichloride                                              22   8.1 (0.016) Dimethylgermyl-                                                                     90 g Ethylene                                                                        60       53   3.02 422.1  2.9                        bisindenylzirconium dichloride                                           23   36.9 (0.073) Ethylenebisindenyl-                                                               110 g Ethylene                                                                        60       240  2.35  15.9  4.4                        hafnium dichloride                                                       24   24.0 (0.046) (Vinyl)(phenyl)-                                                                  110 g Ethylene                                                                        60       60   2.33  97.1  4.4                        silylbisindenylzirconium dichloride                                      __________________________________________________________________________

                                      TABLE 6                                     __________________________________________________________________________    Examples 20-24                                                                (Product properties)                                                                                                                    Enthalpy                                        Drop-                                                                             Mean        Crystal-                                                                           Glass                                                                             Enthalpy                                                                           of                  VN       M.sub.w                                                                           M.sub.n                                                                              AD      ping                                                                              block  Melting                                                                            lization                                                                           trans.                                                                            of   crystal-            [cm.sup.3 /                                                                            [g/ [g/ M.sub.w /                                                                        [g/ MV  point                                                                             length point                                                                              point                                                                              temp.                                                                             fusion                                                                             lization            Example                                                                            g]  mol]                                                                              mol]                                                                              M.sub.n                                                                          dm.sup.3 ]                                                                        [mPa.s]                                                                           [°C.]                                                                      - n.sub.PP                                                                        - n.sub.PE                                                                       [°C.]                                                                       [°C.]                                                                       [°C.]                                                                      [J/g]                                                                              [J/g]               __________________________________________________________________________    20   19.1                                                                              10950                                                                             5065                                                                              2.2                                                                              460 220 124 17.2                                                                              1.02                                                                             109  73   -22 74.0 -58.2               21   29.2                                                                              18650                                                                             8550                                                                              2.2                                                                              470 860 116 12.5                                                                              1.02                                                                             103  63   -22 64.1 - 49.7              22   22.4                                                                              13350                                                                             6600                                                                              2.0                                                                              490 350 133 20.7                                                                              1.04                                                                             119  81   -20 83.7 -71.0               23   19.1                                                                              10750                                                                             3640                                                                              3.0                                                                              450 200 123 14.3                                                                              1.03                                                                             120  84   -30 68.3 -51.8                                (bi-                                                                          mo-                                                                           dal)                                                         24   29.3                                                                              16900                                                                             7350                                                                              2.3                                                                              460 740 124 15.6                                                                              1.02                                                                             107  68   -24 70.2 -56.1               __________________________________________________________________________

                                      TABLE 7                                     __________________________________________________________________________    Examples 25- 27                                                               (Polymerization data)                                                                                                   Amount                                                                             Metallocene                                                              of   activity                                                                             Content of                                mg (mmol)                                                                            Polymerization                                                                         Polymerization                                                                        product                                                                            [kg polymer/                                                                         comonomer units         Example                                                                            g Comonomer  zirconocene                                                                          temperature [°C.]                                                               time [minutes]                                                                        [kg] g cat × h]                                                                     [% by                   __________________________________________________________________________                                                          weight]                 25    200 g 1-Hexen                                                                             8.3 (0.019)                                                                          60       60      1.32 159.0  2.0                     26   1000 g 1-Buten                                                                             8.2 (0.018)                                                                          "        90      1.61 130.9  10.4                    27    500 g 4-Methyl-1-penten                                                                   9.0 (0.020)                                                                          "        60      1.37 152.2  3.6                     __________________________________________________________________________

                                      TABLE 8                                     __________________________________________________________________________    Examples 25-27                                                                (Product properties)                                                                                                                    Enthalpy                                       Drop-            Melt-                                                                             Crystal-                                                                           Enthalpy                                                                           of                      VN  M.sub.w                                                                           M.sub.n                                                                              AD      ping                                                                              Mean block   ting                                                                              lization                                                                           of   crystal-            Ex- [cm.sup.3 /                                                                       [g/ [g/ M.sub.w /                                                                        [g/ MV  point                                                                             length       point                                                                             point                                                                              fusion                                                                             lization            ample                                                                             g]  mol]                                                                              mol]                                                                              M.sub.n                                                                          mol]                                                                              [mPa.s]                                                                           [°C.]                                                                      n.sub.PP                                                                          n.sub.PM                                                                         n.sub.PB                                                                         n.sub.PMP                                                                        [°C.]                                                                      [°C.]                                                                       [J/g]                                                                              [J/g]               __________________________________________________________________________    25  20  10200                                                                             4800                                                                              2.1                                                                              380         100 1.0                                                                              -- -- 127 90   91.4 -78.0               26  18   9870                                                                             4700                                                                              2.1                                                                              390         11.5                                                                              -- 1.10                                                                             -- 115 80   85.1 -74.1               27  17   7650                                                                             3900                                                                              2.0                                                                              400         53.5                                                                              -- -- 1.05                                                                             115 76   79.5 -68.9               __________________________________________________________________________

We claim:
 1. A polypropylene wax comprised of 80 to 99.75% by weight,based on the total polymer, of propylene units and 0.25 to 20% byweight, based on the total polymer, of units which are derived fromethylene or an olefin containing not less than 4 carbon atoms of theformula R¹⁵ --CH═CH--R¹⁶, in which R¹⁵ and R¹⁶ are identical ordifferent and are a hydrogen atom or an alkyl radical containing 1 to 28carbon atoms or R¹⁵ and R¹⁶ form a ring containing 4 to 28 carbon atomswith the carbon atoms joining them, which polypropylene wax has a molarmass M_(w) of 1,000 to 50,000 g/mol, a polydispersity M_(w) /M_(n) of1.8 to 5.0, a viscosity number of 2 to 60 cm³ /g, a melting point of 50°to 150° C., an enthalpy of fusion ΔH of less than 100 J/g, a droppingpoint of 60° to 160° C., a melt viscosity at 170° C. of 100 to 20,000mPa.s and a regular distribution of the comonomer units in the polymerchain, the mean block length n being less than 1.25.
 2. A process forthe production of the polypropylene wax as claimed in claim 1 bypolymerizing 70% to 99.9% by weight, based on the total amount of themonomers, of propylene and 0.1% to 30% by weight, based on the totalamount of the monomers, of not less than one representative of the groupcomprising ethylene and olefins containing not less than 4 carbon atomsof the formula R¹⁵ --CH═CH--R¹⁶, in which R¹⁵ and R¹⁶ have the meaningstated in claim 1, at a temperature of -60° C. to 100° C., at a pressureof 0.5 bar to 120 bar, in solution, in suspension or in the gas phase,in the presence of hydrogen as a molar mass regulator and of a catalystwhich is comprised of a metallocene and an alumoxane wherein thehydrogen partial pressure is 0.05 bar to 50 bar and the molar ratio ofolefin to hydrogen is 3 to 3,000:1, and wherein the metallocene is acompound of the formula I: ##STR11## in which M¹ is metal of the groupIVb, Vb or VIb of the periodic system,R¹ and R² are identical ordifferent and are a hydrogen atoms, a (C₁ -C₁₀)alkyl group, a (C₁-C₁₀)alkoxy group, a (C₆ -C₁₀)aryl group, a (C₆ -C₁₀)aryloxy group, a(C₂ -C₁₀)alkenyl group, a (C₇ -C₄₀)arylalkyl group, a (C₇ -C₄₀)alkylarylgroup, a (C₈ -C₄₀)arylalkenyl group or a halogen atom, R³, R⁴, R⁵ and R⁶are identical or different and are a hydrogen atom, a halogen atom, a(C₁ -C₁₀)alkyl group, a (C₆ -C₁₀)aryl group, a (C₁ -C₁₀)alkoxy group, oran --NR¹⁰ ₂₉, --SR¹⁰, --OSiR¹⁰ ₃, --SiR¹⁰ ₃, or --PR¹⁰ ₂ radical, inwhich R¹⁰ is a (C₁ -C₁₀)alkyl group, a (C₆ -C₁₀)aryl group oralternatively, in the case of radicals containing silicon or phosphorus,a halogen atom, or two adjacent radicals R³, R⁴, R⁵ or R⁶ each form aring with the carbon atoms joining them, R⁷ is ##STR12## ═BR¹¹, ═AlR¹¹,--Ge--, --Sn--, --O--, --S--, ═SO, ═SO₂, ═NR¹¹, ═CO, ═PR¹¹ or ═P(O)R¹¹whereR¹¹, R¹² and R¹³ are identical or different and are a hydrogenatom, a halogen atom, a (C₁ -C₃₀)alkyl group, a (C₁ -C₁₀)fluoroalkylgroup, a (C₆ -C₁₀)aryl group, a (C₆ -C₁₀)fluoroaryl group, a (C₁-C₁₀)alkoxy group, a (C₂ -C₁₀)alkenyl group, a (C₇ -C₄₀)arylalkyl group,a (C₈ -C₄₀)arylalkenyl group, a (C₇ -C₄₀)alkylaryl group, or R¹¹ and R¹²or R¹¹ and R¹³ in each case form a ring with the atoms joining them, M²is silicon, germanium or tin, R⁸ and R⁹ are identical or different andhave the meaning stated for R¹¹, m and n are identical or different andare zero, 1 or 2, m plus n being zero, 1 or 2, and the alumoxane is acompound of the formula (II): ##STR13## for the linear type and/or ofthe formula (III) ##STR14## for the cyclic type, R¹⁴ being a (C₁-C₆)alkyl group in the formulae (II) and (III) and p being an integerfrom 2 to
 50. 3. The process of claim 2, wherein said olefin is1-butene, 1-hexene, 4-methyl-1-pentene, 1-pentene, 1-octene, norbornene,norbornadiene, 6-pentene, cyclohexane or cyclooctene.
 4. Thepolypropylene wax of claim 1, wherein said molar mass M_(w) ranges from8,000 to 45,000 g/mol.
 5. The polypropylene wax of claim 1, wherein saidpolydispersity M_(w) /M_(n) ranges in value from 2.0 to 4.0.
 6. Thepolypropylene wax of claim 1, wherein said viscosity ranges in valuefrom 10 cm³ /g to 50 cm³ /g.
 7. The polypropylene wax of claim 1,wherein said melting point ranges in value from 70° C. to 140° C.
 8. Thepolypropylene wax of claim 1, wherein said dropping point ranges invalue from 80° C. to 150° C.
 9. The polypropylene wax of claim 1,wherein said melt viscosity ranges in value from 120 mPa.s to 7,000mPa.s at 170° C.
 10. The polypropylene wax of claim 1, wherein said n isless than 1.2.
 11. The process of claim 2, wherein said M¹ is zirconiumor hafnium.
 12. The process of claim 2, wherein said R¹ and R² areidentical or different and are a (C₁ -C₃)alkyl group, a (C₁ -C₃)alkoxygroup, a (C₆ -C₈)aryl group, a (C₆ -C₈)aryloxy group, a (C₂ -C₄)alkenylgroup, a (C₇ -C₁₀)arylalkyl group, a (C₇ -C₁₂)alkylaryl group, a (C₈-C₁₂)arylalkenyl group or a chlorine.
 13. The process of claim 2,wherein said R³, R⁴, R⁵ and R⁶ are identical or different and are afluorine, chlorine or bromine atom, a (C₁ -C₃)alkyl group, a (C₆-C₈)aryl group, of a (C₁ -C₃)alkoxy group.
 14. The process of claim 2,wherein said R¹⁰ is a (C₁ -C₃)alkyl group, or a (C₆ -C₈)aryl group. 15.The process of claim 2, wherein said R¹¹, R¹², and R¹³ are identical ordifferent and a (C₁ -C₄)alkyl group, a methyl group, a CF₃ group, apentafluorophenyl group, a (C₆ -C₈)aryl group, a (C₁ -C₄)alkoxy group, amethoxy group, a (C₂ -C₄)alkenyl group, a (C₇ -C₁₀)arylalkyl group, a(C₈ -C₁₂)arylalkenyl group, or a (C₇ -C₁₂)alkylaryl group.
 16. Theprocess of claim 2, wherein said M² is silicon or germanium.
 17. Theprocess of claim 2, wherein said R⁷ is ═CR¹¹ R¹², ═SiR¹¹ R¹², ═GeR¹¹R¹², --O--, --S--, ═SO, ═PR¹¹ or ═P(O)R¹¹.
 18. The process of claim 2,wherein said m and n are zero or 1, and m plus n is zero or 1.